Methods and systems for acquiring and presenting two-dimensional and three-dimensional images are known in the art. Three-dimensional imaging enhances modern diagnostics, therapy and surgery procedures.
A two-dimensional imaging system processes and represents two-dimensional internal body slices in static or in dynamic form on a display. A conventional two-dimensional ultrasound imaging system includes an ultrasound transducer, an image capturing module and an image-processing unit.
The ultrasound transducer is placed in close proximity to the tissue to be examined. The ultrasound transducer converts an electrical signal to ultrasonic waves and directs the waves toward the examined tissue. The ultrasonic waves are in part absorbed, dispersed, refracted and reflected. The ultrasound transducer detects the ultrasonic reflections. The ultrasound transducer converts the reflected ultrasonic waves to an electrical signal and provides it to the image-processing unit.
The image-processing unit processes the received electrical signal, thereby producing a plurality of two-dimensional images of slices of the inspected tissue. The image-capturing module captures each two-dimensional image and can provide each of them to a display or a printer.
U.S. Pat. No. 5,152,290 to Freeland, entitled “Method for recording ultrasound images to diagnose heart and coronary artery disease” is directed to a method for capturing and displaying two-dimensional ultrasound images of the heart for diagnosing heart disease, such as coronary artery disease. The method disclosed by Freeland includes the procedures of detecting an electrocardiogram (ECG) signal after peak exercise, detecting the two-dimensional images of the heart, storing selected images, each with the ECG reading at the time that the image was taken and displaying a quad-image group. The system detects and records a two-dimensional image sequence continuously at a rate of at least eight images per heartbeat.
U.S. Pat. No. 5,690,113, issued to Sliwa, Jr. et al., entitled “Method and apparatus for two-dimensional ultrasonic imaging” is directed to a method and apparatus for generating a two-dimensional ultrasonic image using a hand-held single element transducer probe, having a fixed scan-line. The system provides displaying two-dimensional ultrasonic images of the body of a patient. This system detects two-dimensional ultrasonic images, and determines the spatial location and orientation of the ultrasound transducer, at the same time. The system includes a probe with an ultrasound transducer, capable of imaging a single scan-line and a means for tracking the spatial location and orientation of the ultrasound transducer. The scan-line is fixed in an orientation and spatial position relative to the movable transducer. The system further includes a computing means, which computes the spatial location and the orientation of each scan-line as the transducer is moved. Thereby, the scan-lines are presented as a complete image. Alternatively, an electromagnetic transmitter and a receiving sensor determine the spatial orientation and position of each scan-line in free space.
A typical three-dimensional ultrasound imaging system includes a conventional two-dimensional ultrasound imaging system, a location and orientation detection system, an image processing system and a displaying system. Such systems provide three-dimensional imaging of internal organs such as the liver, kidneys, gallbladder, breast, eyes, brain, and the like.
The location and orientation detection system provides the location and orientation of ultrasound transducer. The location and orientation of each of the captured two-dimensional images are determined from the location and orientation of the transducer.
The image processing system reconstructs a three-dimensional image of the inspected organ, by processing the captured two-dimensional images, each according to the location and orientation thereof. Finally, the displaying system displays the received three-dimensional image of the inspected organ.
U.S. Pat. No. 5,787,889 issued to Edwards et al., and entitled “Ultrasound imaging with real time 3D image reconstruction and visualization” is directed to generation and visualization of three-dimensional ultrasound images. The method disclosed by Edwards includes the following procedures: acquiring data, reconstructing a volume, and visualizing an image. The system provides for achieving and visualizing three-dimensional ultrasound images with a two-dimensional ultrasound medical imaging system included therein. An operator can perform various visualization tasks on the reconstructed three-dimensional image, such as rotating the image in different viewing angles and plans.
Another type of three-dimensional imaging system, which is known in the art, is operative to produce a motion picture of the heart or the lungs. This system includes a conventional two-dimensional ultrasound imaging system, an ECG monitor, a location and orientation detection system, an image processor and a display system. The ECG monitor detects the timing signal of the heart. The ECG timing signal is used to synchronize or trigger the recording of the two-dimensional images representative of selected points in the ECG timing signal. The ultrasound transducer detects two-dimensional ultrasound images of the heart at any given moment (e.g., at a selected point of time on ECG timing signal). Each two-dimensional image represents a specific slice of the heart according to the specific activity-state thereof. The location and orientation of each of the two-dimensional images are directly determined from the location and orientation of the transducer.
The image processor reconstructs a three-dimensional image of the heart from captured two-dimensional images having the same activity-state. Finally, the display system displays a sequence of the reconstructed images, thereby presenting a three-dimensional motion picture of the heart.
U.S. Pat. No. 5,924,989 issued to Polz, and entitled “Method and device for capturing diagnostically acceptable three-dimensional ultrasound image data records”, is directed to a method and a system for generating a three-dimensional image sequence of the heart. This system includes a three-dimensional ultrasound imaging system, combined with an echocardiograph. The system detects two-dimensional ultrasound images and stores each of them together with the location and orientation thereof and with the organ cycle location as provided by the echocardiogram, at the time that the image was acquired. Utilizing a special algorithm, the system reconstructs a three-dimensional image from all of the two-dimensional images having the same organ cycle location, and displays a sequence of the reconstructed three-dimensional images.
U.S. Pat. No. 5,830,145 issued to Tenhoff and entitled “Enhanced Accuracy of Three-Dimensional Intraluminal Ultrasound (ILUS) Image Reconstruction”, is directed to a system and a method for imaging an organ within a body. The system of Tenhoff is described herein below, with reference to FIGS. 13A and 13B.
FIG. 13A is a schematic illustration of a system for displaying a three-dimensional image of an organ, generally referenced 10, which is known in the prior art. FIG. 13B is a schematic illustration of the trajectory of the imaging tip of the catheter of the system of FIG. 13A, inside an artery of the patient.
With reference to FIG. 13A, system 10 includes a catheter 12, an automatic pull-back device 14, a processing system 16, a chest harness 18 and a catheter tracking system (not shown). The proximal end of catheter 12 includes a handle 20. Processing system 16 includes a control console, an ultrasound transceiver and a display. Catheter 12 includes a catheter imaging tip (not shown) located at the distal end thereof. The catheter imaging system is an intraluminal ultrasound (ILUS) transducer (not shown). The catheter tracking system includes at least one tracking transducer (not shown), mounted on catheter 12 and typically adjacent the catheter imaging tip. The catheter tracking system further includes a plurality of reference frame transducers located within chest harness 18. Each of the tracking transducers and the reference frame transducers, is an ultrasound transducer. The reference frame transducers define the origin of a global coordinate system. In another embodiment of the patent, the catheter imaging system is an optical coherence tomography (OCT) imaging system.
Handle 20 is coupled to automatic pull-back device 14. The reference frame transducers are coupled to processing system 16 by wires 24. The tracking transducers are coupled to processing system 16 by wires 26. The catheter imaging system is coupled to processing system 16 by wires 28. Automatic pull-back device 14 is coupled to processing system 16 by wires 30.
The operator (not shown) enters catheter 12 in the body of a patient 22 through the femoral artery and positions catheter 12 within a region of interest (e.g., the coronary arteries). The catheter imaging system provides a plurality of two-dimensional images (e.g., echographic images in case of an ILUS transducer) of the area which surrounds the catheter imaging tip, when the catheter imaging tip is located in the region of interest.
The catheter imaging system is carried through a pull-back sequence, optionally using automatic pull-back device 14. The echographic data sets obtained during pull-back, provide the necessary input to produce an image to be displayed on the display. During the pull-back of the catheter imaging tip, processing system 16 records the position (X, Y, Z) and the time at each interval for which data is recorded.
The angulation in three dimensional space of the catheter imaging tip, for each image, is determined by using the coordinates of one or more of the tracking transducers. A pair of transducers marks the location of the catheter imaging tip during the pull-back. The pair of closely spaced transducers define a line which calculates the tangent to the curve defined by the catheter imaging tip at that point. The tangent is calculated by the line defined by the two or more points determined by the location of the tracking transducers.
In another embodiment of the patent, a single marker transducer is employed to mark the location of the catheter imaging tip during pull-back. In this case, the tangent is calculated by the line through two points determined by the successive locations of the marker transducer at two positions during the pull-back.
Processing system 16 uses the coordinates (X, Y, Z) of each echographic image acquired along the catheter pull-back path, in conjunction with the time data, to reconstruct a three-dimensional image. Each three-dimensional image is reconstructed by stacking the echographic images around the catheter pull-back trajectory.
With further reference to FIG. 13B, processing system 16 (FIG. 13A) generates a trajectory 50 of the imaging tip of catheter 12 during pull-back and the display displays trajectory 50 with reference to the origin of the global coordinate system. Trajectory 50 is defined by a plurality of points in the global coordinate system, such as points 52, 54, 56, 58, 60, 62, 64, 66 and 68. Each of the points 52, 54, 56, 58, 60, 62, 64, 66 and 68 corresponds to a different position of the catheter imaging tip during pull-back.
However, it is noted that during the pull-back sequence, the artery constantly moves to different positions such as positions 70, 72 and 74, and the location and orientation of the artery with respect to the origin of the global coordinate system, changes. Thus, trajectory 50 of catheter 12 does not represent the true trajectory of catheter 12 within the artery and trajectory 50 is substantially inaccurate.
Optical Coherence Tomography (OCT) is a general name for a method optically scans through tissue at very high resolution. OCT measures the intensity of back-reflected infrared light and yields imaging resolution, which is 5-25 times greater than other current clinical imaging technologies, such as ultrasound.
U.S. Pat. No. 6,134,003 to Tearney et al., entitled “Method and apparatus for performing optical measurements using a fiber optic imaging guidewire, catheter or endoscope”, U.S. Pat. No. 6,175,669 to Colston et al., entitled “Optical coherence domain reflectometry guidewire” and U.S. Pat. No. 5,994,690 to Kulkami et al., entitled “Image enhancement in optical coherence tomography using deconvolution” are all directed to methods and system using OCT imaging technology.
Intra-vascular plaques may be prone to rupture and may provoke fatal vessel obstruction. These plaques often exhibit a different temperature than other inner vessel structures and hence, can be detected and consequently treated according to a temperature map of the inner layers of the vessel. Methods and systems for intra-vascular temperature mapping are known in the art, and are conventionally based on Infrared technology, using optic fibers, which are inserted into the blood vessel, for detecting “hot” plaques. This technique is called thermography. U.S. Pat. No. 5,935,075 to Casscells et al., entitled “Detecting Thermal Discrepancies in Vessel Walls” is directed to a system for analyzing optical radiation in blood vessels, which attempts to detect “hot” plaques.